Multi-function synthetic jet and method of manufacturing same

ABSTRACT

A synthetic jet assembly includes a synthetic jet having a cavity and an opening formed therein. The synthetic jet assembly also includes an actuator element coupled to a second surface of the body to selectively cause displacement of the second surface, and a control unit electrically coupled to the actuator element. The control unit is configured to transmit a multi-frequency drive signal to the actuator element, the multi-frequency drive signal comprising a cooling frequency component and an acoustic frequency component superimposed on the cooling frequency component. The cooling frequency component causes a cooling jet to eject from the opening of the body. The acoustic frequency component produces a desired audible output.

BACKGROUND OF THE INVENTION

Embodiments of the invention relate generally to synthetic jets and,more particularly, to multi-function synthetic jets.

Synthetic jet actuators are a widely-used technology that generates asynthetic jet of fluid to influence the flow of that fluid over asurface. A typical synthetic jet actuator comprises a housing definingan internal chamber. An orifice is present in a wall of the housing. Theactuator further includes a mechanism in or about the housing forperiodically changing the volume within the internal chamber so that aflow is generated and projected in an external environment out from theorifice of the housing. This flow can include fluid vortices. Examplesof volume changing mechanisms may include, for example, a pistonpositioned in the jet housing to move fluid in and out of the orificeduring reciprocation of the piston or a flexible diaphragm as a wall ofthe housing. The flexible diaphragm is typically actuated by apiezoelectric actuator or other appropriate means.

Typically, a system is used to create time-harmonic motion of the volumechanging mechanism. As the mechanism decreases the chamber volume, fluidis ejected from the chamber through the orifice. As the fluid passesthrough the orifice, sharp edges of the orifice separate the flow tocreate vortex sheets that roll up into vortices. These vortices moveaway from the edges of the orifice under their own self-inducedvelocity. As the mechanism increases the chamber volume, ambient fluidis drawn into the chamber from large distances from the orifice. Sincethe vortices have already moved away from the edges of the orifice, theyare not affected by the ambient fluid entering into the chamber. As thevortices travel away from the orifice, they synthesize a jet of fluid,i.e., a “synthetic jet.”

To improve the heat transfer path, micro/meso scale devices such assynthetic jets have been proposed as a possible replacement for oraugmentation of natural convection in microelectronics devices.Applications may include impingement of a fluid in and around theelectronics and printed circuit boards. However, a synthetic jettypically a number of natural frequencies at which the synthetic jetyields superior cooling performance. These natural frequencies includethe structural resonant frequency. The structural resonant frequency iscaused at the natural frequency of the structure of the synthetic jet,which consists typically of the synthetic jet plates acting as a massand the elastomeric wall acting as a spring coupled with the air in thesynthetic jet volume.

One major use for synthetic jets is in the cooling of heat-producingbodies, which is a concern in many different technologies. As oneexample, a synthetic jet may be used for thermal management of tightspaces where electronics may be housed and where space for theelectronics is a premium. Typically, wireless communication devices suchas cellular phones, pagers, two-way radios, and the like, have much oftheir heat generated in integrated circuit (i.e., IC) packages that arepositioned in such tight spaces. Because of the limited space andlimited natural convection therein, the heat generated is typicallyconducted into printed circuit boards and then transferred to thehousing interior walls via conduction, convection, and radiativeprocesses. The heat is then typically conducted through the housingwalls and to the surrounding ambient environment. The process istypically limited because of the limited opportunity for convectioncooling within the housing and over the printed circuit boards. The lowthermal conductivity of the fiberglass epoxy resin-based printed circuitboards can lead to high thermal resistance between the heat source andthe ambient environment. And, with the advent of smaller enclosures,higher digital clock speeds, greater numbers of power-emitting devices,higher power-density components, and increased expectations forreliability, thermal management issues present an increasing challengein microelectronics applications.

Typical electronic devices and integrated circuit packages includenumerous components to achieve their desired function, such as coolingdevices, microphones, speakers, control circuitry, memory devices, andthe like. While the use of a synthetic jet over an alternative coolingdevice, such as an air-cooling fan, saves space within the IC package,advancements in IC packaging are driven by ever-increasing needs forgreater miniaturization of electronics packaging and the componentstherein.

Accordingly, there is a need for a simplified method and apparatus forproviding cooling of integrated circuits while minimizing the overallsize and complexity of the electronic device.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with one aspect of the invention, a synthetic jet assemblyincludes a synthetic jet having a cavity and an opening formed therein,an actuator element coupled to a second surface of the body toselectively cause displacement of the second surface, and a control unitelectrically coupled to the actuator element. The control unit isconfigured to transmit a multi-frequency drive signal to the actuatorelement, the multi-frequency drive signal comprising a cooling frequencycomponent and an acoustic frequency component superimposed on thecooling frequency component. The cooling frequency component causes acooling jet to eject from the opening of the body. The acousticfrequency component produces a desired audible output.

In accordance with another aspect of the invention, a method ofmanufacturing a synthetic jet assembly includes providing a syntheticjet body that encircles a volume, forming an orifice in the syntheticjet body to fluidically couple the volume to a gas outside the volume,coupling an actuator element to a flexible surface of the synthetic jetbody, and electronically coupling a controller assembly to the actuatorelement. The controller assembly is programmed to generate a first drivesignal comprising an inaudible frequency component that causes a coolingjet to expel from the orifice, generate a second drive signal comprisingan audible frequency component that generates a desired acoustic output,combine the first and second drive signals to form a combined drivesignal, and transmit the combined drive signal to the actuator element.

In accordance with yet another aspect of the invention, an electronicapparatus includes a synthetic jet including a housing having an orificeformed therein for introducing a fluid from outside the housing into acavity of the housing and expelling a cooling jet therefrom and apiezoelectric actuator coupled to the housing. The electronic apparatusalso includes a drive unit configured to drive the piezoelectricactuator, a control unit configured to transmit a multi-frequency drivesignal to the drive unit, and an electronic component configured to becooled by the cooling jet. The multi-frequency drive signal includes acooling frequency component selected to generate the cooling jet and afrequency component selected to generate an audible acoustic output.

Various other features and advantages will be made apparent from thefollowing detailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate embodiments presently contemplated for carryingout the invention.

In the drawings:

FIG. 1 is a perspective view of a synthetic jet assembly according to anembodiment of the invention.

FIG. 2 is a cross-section of a portion of a synthetic jet according toan embodiment of the invention.

FIG. 3 is a cross-section of the synthetic jet of FIG. 2 depicting thejet as the control system causes the diaphragms to travel inward, towardthe orifice.

FIG. 4 is a cross-section of the synthetic jet actuator of FIG. 2depicting the jet as the control system causes the diaphragms to traveloutward, away from the orifice.

FIG. 5 is a block schematic diagram of a control system and syntheticjet according to an embodiment of the invention.

FIG. 6 is a frequency diagram of an exemplary drive signal for thesynthetic jet of FIG. 2 according to an embodiment of the invention.

FIG. 7 is a block schematic diagram of a control system and syntheticjet according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the invention relate to a piezoelectric motive device andmethods of making and using a piezoelectric motive device tosimultaneously generate a fluid jet and a desired audio output. Theoperating environment is described herein with respect to a thermalmanagement system for enhancing convection in cooling of electronics.However, it will be appreciated by those skilled in the art thatembodiments of the invention are equally applicable for use with othersynthetic jet applications. For instance, synthetic jets have beenroutinely used for stand-point flow control, thrust vectoring of jets,triggering turbulence in boundary layers, and other heat transferapplications. Heat transfer applications may include direct impingementof vortex dipoles on heated surfaces and employing synthetic jets toenhance the performance of existing cooling circuits. Thus, althoughembodiments of the invention are described with respect to cooling ofelectronics, they are equally applicable to systems and applicationsusing synthetic jets for other purposes.

Referring to FIG. 1, a perspective view of a synthetic jet assembly 10is provided. Synthetic jet assembly 10 includes a synthetic jet 12, across-section of which is illustrated in FIG. 2, and a mounting device14. In one embodiment, mounting device 14 is a u-shaped bracket that isaffixed to a housing 16 of synthetic jet 12 at one or more locations. Acircuit driver 18 can be externally located or affixed to mountingdevice 14. Alternatively, circuit driver 18 may be remotely located fromsynthetic jet assembly 10.

Referring now to FIGS. 1 and 2 together, housing 16 of synthetic jet 12defines and partially encloses an internal chamber or cavity 20 having agas or fluid 22 therein. While housing 16 and internal chamber 20 cantake virtually any geometric configuration according to variousembodiments of the invention, for purposes of discussion andunderstanding, housing 16 is shown in cross-section in FIG. 2 asincluding a first plate 24 and a second plate 26, which are maintainedin a spaced apart relationship by a spacer element 28 positionedtherebetween. In one embodiment, spacer element 28 maintains aseparation of approximately 1 mm between first and second plates 24, 26.One or more orifices 30 are formed between first and second plates 24,26 and the side walls of spacer element 28 in order to place theinternal chamber 20 in fluid communication with a surrounding, exteriorenvironment 32. In an alternative embodiment, spacer element 28 includesa front surface (not shown) in which one or more orifices 30 are formed.

According to various embodiments, first and second plates 24, 26 may beformed from a metal, plastic, glass, and/or ceramic. Likewise, spacerelement 28 may be formed from a metal, plastic, glass, and/or ceramic.Suitable metals include materials such as nickel, aluminum, copper, andmolybdenum, or alloys such as stainless steel, brass, bronze, and thelike. Suitable polymers and plastics include thermoplastics such aspolyolefins, polycarbonate, thermosets, epoxies, urethanes, acrylics,silicones, polyimides, and photoresist-capable materials, and otherresilient plastics. Suitable ceramics include, for example, titanates(such as lanthanum titanate, bismuth titanate, and lead zirconatetitanate) and molybdates. Furthermore, various other components ofsynthetic jet 12 may be formed from metal as well.

Actuators 34, 36 are coupled to respective first and second plates, 24,26 to form first and second composite structures or flexible diaphragms38, 40, which are controlled by driver 18 via a controller assembly orcontrol unit system 42. As shown in FIG. 1, in one embodiment controllerassembly 42 is electronically coupled to driver 18, which is coupleddirectly to mounting bracket 14 of synthetic jet 12. In an alternativeembodiment control unit system 42 is integrated into a driver 18 that isremotely located from synthetic jet 12. For example, each flexiblediaphragm 38, 40 may be equipped with a metal layer and a metalelectrode may be disposed adjacent to the metal layer so that diaphragms38, 40 may be moved via an electrical bias imposed between the electrodeand the metal layer. Moreover, control system 42 may be configured togenerate the electrical bias by any suitable device, such as, forexample, a computer, logic processor, or signal generator.

In one embodiment, actuators 34, 36 are piezoelectric motive(piezomotive) devices that may be actuated by application of a harmonicalternating voltage that causes the piezomotive devices to rapidlyexpand and contract. During operation, control system 42 transmits anelectric charge, via driver 18, to piezoelectric actuators 34, 36, whichundergo mechanical stress and/or strain responsive to the charge. Thestress/strain of piezomotive actuators 34, 36 causes deflection ofrespective first and second plates 24, 26 such that a time-harmonic orperiodic motion is achieved. The resulting volume change in internalchamber 20 causes an interchange of gas or other fluid between internalchamber 20 and exterior volume 32, as described in detail with respectto FIGS. 3 and 4.

Piezomotive actuators 34, 36 may be monomorph or bimorph devices,according to various embodiments of the invention. In a monomorphembodiment, piezomotive actuators 34, 36 may be coupled to plates 24, 26formed from materials including metal, plastic, glass, or ceramic. In abimorph embodiment, one or both piezomotive actuators 34, 36 may bebimorph actuators coupled to plates 24, 26 formed from piezoelectricmaterials. In an alternate embodiment, the bimorph may include singleactuators 34, 36, and plates 24, 26 are the second actuators.

The components of synthetic jet 12 may be adhered together or otherwiseattached to one another using adhesives, solders, and the like. In oneembodiment, a thermoset adhesive or an electrically conductive adhesiveis employed to bond actuators 34, 36 to first and second plates, 24, 26to form first and second composite structures 38, 40. In the case of anelectrically conductive adhesive, an adhesive may be filled with anelectrically conductive filler such as silver, gold, and the like, inorder to attach lead wires (not shown) to synthetic jet 12. Suitableadhesives may have a hardness in the range of Shore A hardness of 100 orless and may include as examples silicones, polyurethanes, thermoplasticrubbers, and the like, such that an operating temperature of 120 degreesor greater may be achieved.

In an embodiment of the invention, actuators 34, 36 may include devicesother than piezoelectric motive devices, such as hydraulic, pneumatic,magnetic, electrostatic, and ultrasonic materials. Thus, in suchembodiments, control system 42 is configured to activate respectiveactuators 34, 36 in corresponding fashion. For example, if electrostaticmaterials are used, control system 42 may be configured to provide arapidly alternating electrostatic voltage to actuators 34, 36 in orderto activate and flex respective first and second plates 24, 26.

The operation of synthetic jet 12 is described with reference to FIGS. 3and 4. Referring first to FIG. 3, synthetic jet 12 is illustrated asactuators 34, 36 are controlled to cause first and second plates 24, 26to move outward with respect to internal chamber 20, as depicted byarrows 44. As first and second plates 24, 26 flex outward, the internalvolume of internal chamber 20 increases, and ambient fluid or gas 46rushes into internal chamber 20 as depicted by the set of arrows 48.Actuators 34, 36 are controlled by control system 42 so that when firstand second plates 24, 26 move outward from internal chamber 20, vorticesare already removed from edges of orifice 30 and thus are not affectedby the ambient fluid 46 being drawn into internal chamber 20. Meanwhile,a jet of ambient fluid 46 is synthesized by vortices creating strongentrainment of ambient fluid 46 drawn from large distances away fromorifice 30.

FIG. 4 depicts synthetic jet 12 as actuators 34, 36 are controlled tocause first and second plates 24, 26 to flex inward into internalchamber 20, as depicted by arrows 50. The internal volume of internalchamber 20 decreases, and fluid 22 is ejected as a cooling jet throughorifice 30 in the direction indicated by the set of arrows 52 toward adevice 54 to be cooled, such as, for example a light emitting diode. Asthe fluid 22 exits internal chamber 20 through orifice 30, the flowseparates at the sharp edges of orifice 30 and creates vortex sheetswhich roll into vortices and begin to move away from edges of orifice30.

While the synthetic jet of FIGS. 1-4 is shown and described as having asingle orifice therein, it is also envisioned that embodiments of theinvention may include multiple orifice synthetic jet actuators.Additionally, while the synthetic jet actuators of FIGS. 1-4 are shownand described as having an actuator element included on each of firstand second plates, it is also envisioned that embodiments of theinvention may include only a single actuator element positioned on oneof the plates. Furthermore, it is also envisioned that the synthetic jetplates may be provided in a circular, rectangular, or alternativelyshaped configuration, rather than in a square configuration asillustrated herein.

Referring now to FIG. 5, a block schematic diagram of synthetic jet 12and control system 42 is provided according to one embodiment of theinvention. In operation, control system 42 is programmed to transmit amulti-frequency drive signal 56 to actuators 34, 36 (FIG. 2) ofsynthetic jet 12. Multi-frequency drive signal 56 is a combined drivesignal generated from a combination of a cooling frequency drive signal58, which is used to generate a cooling jet, and an acoustic frequencydrive signal 60, which is used to generate a desired audio output.

Drive signals 58, 60 are combined by a controller 62 having a digitalsignal processing (DSP) algorithm stored thereon. Controller 62 receivesthe cooling and acoustic frequency drive signals 58, 60 and inputs thesignals to the DSP algorithm in order to generate multi-frequency drivesignal 56, which has a cooling frequency component from drive signal 58and an acoustic frequency component from drive signal 60. The coolingfrequency component of multi-frequency drive signal 56 causes syntheticjet 12 to expand and contract in a manner that generates a desired jetfor cooling purposes. In one embodiment, the cooling frequency componentapplies an AC voltage to synthetic jet 12 at a frequency thatundetectable or virtually undetectable by a human ear, such as, forexample, between approximately 10 and 400 hertz or alternatively above20,000 hertz. The acoustic frequency component of multi-frequency drivesignal 56 causes synthetic jet 12 to generate an audible acoustic outputthat is detectable by, for example, a human ear. According to variousembodiments, the acoustic frequency component may apply an AC voltage atone or more frequencies between approximately 500 and 20,000 hertz. Asshown in detail in FIG. 6, the acoustic frequency component ofmulti-frequency drive signal 56 is superimposed on the cooling frequencycomponent. Thus, the multi-frequency drive signal 56 generatessimultaneous cooling and audible acoustic output.

Referring back to FIG. 5, control system 42 generates a multi-frequencydrive signal 56 that drives synthetic jet 12 in one of an audio-outputmode or a noise-cancelling mode while maintaining the driving frequencyfor cooling. As used herein, audio-output mode refers to an operatingmode wherein the acoustic frequency component causes synthetic jet 12 togenerate a desired audible acoustic output such as, for example, averbal announcement, an alarm, a server message, or musical output. Asused herein, noise-cancelling mode refers to an operating mode whereinthe acoustic frequency component causes synthetic jet 12 to generate adesired audible acoustic output that cancels or mitigates an undesiredambient noise condition.

When operating in an audio-output mode, the actuating elements 34, 36 ofsynthetic jet 12 are driven to generate an acoustic output that can beused for audio applications in devices equipped with synthetic jets forcooling operations. Thus, synthetic jet 12 operates as both a coolingdevice and speaker. In such an embodiment, in addition to providingactive cooling, synthetic jet 12 may be used in any number ofapplications, including for example, as an alternative to simultaneouslyfunction as a speaker in consumer electronic devices such as a cellulartelephone, to output an audible alert or serve messages, for buildingannouncements, or to generate ambient music in lighting applications. Inaudio-output mode the acoustic frequency component may include, forexample, one or multiple frequencies in a range of approximately500-4,000 hertz.

In one embodiment of noise-cancelling mode, control system 42 ispre-programmed with an acoustic anti-noise drive signal 60 correspondingto one or more known tonal frequencies of an undesirable environmentalnoise or ambient noise condition. For example, the anti-noise drivesignal 60 may be selected to cancel audible acoustic noise generated byan engine, fan, or other noise generating apparatus located in thevicinity of synthetic jet 12. In such an embodiment, anti-noise drivesignal 60 is produced by phase shifting the ambient noise by generatingan anti-noise drive signal 60 is approximately 180 degrees out of phasefrom the ambient noise, for example. The synthetic jet 12 cansimultaneously provide cooling while providing anti-noise.

Referring now to FIG. 7, a block schematic diagram of synthetic jet 12and control system 42 is illustrated according to of the inventionwherein control system 42 is configured to drive synthetic jet 12 in analternative embodiment of noise-cancelling mode. In such mode, controlsystem 42 drives actuating elements 34, 36 (FIG. 2) of synthetic jet 12at an acoustic frequency to generate anti-noise using an acoustic drivesignal that cancels or mitigates a measured or recorded ambient noisewhile simultaneously providing cooling, as described in detail below.

One or more sound detection units 64, such as microphones, are used tomeasure/record the ambient acoustic noise 66. A digital signal 68corresponding to the measured/recorded noise 66 is output to acontroller 70 having a digital signal processing (DSP) algorithm storedthereon. Controller 70 receives the output from microphone(s) 64 andinputs it to the DSP algorithm in order to determine an anti-noise drivesignal 72 having a proper frequency and phase at which anti-noise shouldbe generated by synthetic jet 12, such as, for example, one or morefrequencies that are shifted approximately 180 degrees out of phase ofthe detected noise. In one embodiment, the anti-noise drive signal 72may be determined based on identified frequencies above or below apredefined threshold. Further, the anti-noise drive signal 72 may usedto effectively shift one or more tonal frequencies or a given frequencyspectrum.

In a similar manner as described with respect to FIG. 5, controller 62then combines a cooling-frequency drive signal 58 for cooling purposeswith the anti-noise drive signal 72 to generate a multi-frequency drivesignal 74 having a cooling-frequency component corresponding to drivesignal 58 and an acoustic-frequency component corresponding to drivesignal 72. Actuating elements 34, 36 (FIG. 2) then drive synthetic jet12 both at a desired cooling frequency and at a frequency correspondingto that of the ambient acoustic noise, but that is out of phasetherewith, so as to mitigate or cancel the undesirable ambient noise.Thus, by controller operation of synthetic jet 12 by way of the DSPalgorithms of controllers 62, 70, synthetic jet 12 is able to activelygenerate anti-noise at a plurality of different tonal frequencies whilemaintaining active cooling.

While the waveforms of the various drive signals described herein areillustrated as sine waves, it should be appreciated that the drivesignals are not to be limited to any specific waveform and may beprovided as a sine wave, a square wave, a triangular wave, or any othersuitable waveform.

Therefore, according to one embodiment of the invention, a synthetic jetassembly includes a synthetic jet having a cavity and an opening formedtherein, an actuator element coupled to a second surface of the body toselectively cause displacement of the second surface, and a control unitelectrically coupled to the actuator element. The control unit isconfigured to transmit a multi-frequency drive signal to the actuatorelement, the multi-frequency drive signal comprising a cooling frequencycomponent and an acoustic frequency component superimposed on thecooling frequency component. The cooling frequency component causes acooling jet to eject from the opening of the body. The acousticfrequency component produces a desired audible output.

According to another embodiment of the invention, a method ofmanufacturing a synthetic jet assembly includes providing a syntheticjet body that encircles a volume, forming an orifice in the syntheticjet body to fluidically couple the volume to a gas outside the volume,coupling an actuator element to a flexible surface of the synthetic jetbody, and electronically coupling a controller assembly to the actuatorelement. The controller assembly is programmed to generate a first drivesignal comprising an inaudible frequency component that causes a coolingjet to expel from the orifice, generate a second drive signal comprisingan audible frequency component that generates a desired acoustic output,combine the first and second drive signals to form a combined drivesignal, and transmit the combined drive signal to the actuator element.

According to yet another embodiment of the invention, an electronicapparatus includes a synthetic jet including a housing having an orificeformed therein for introducing a fluid from outside the housing into acavity of the housing and expelling a cooling jet therefrom and apiezoelectric actuator coupled to the housing. The electronic apparatusalso includes a drive unit configured to drive the piezoelectricactuator, a control unit configured to transmit a multi-frequency drivesignal to the drive unit, and an electronic component configured to becooled by the cooling jet. The multi-frequency drive signal includes acooling frequency component selected to generate the cooling jet and afrequency component selected to generate an audible acoustic output.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A synthetic jet assembly comprising: a syntheticjet comprising: a body having a cavity and an opening formed therein; anactuator element coupled to a second surface of the body to selectivelycause displacement of the second surface; and a control unitelectrically coupled to the actuator element, the control unitconfigured to transmit a multi-frequency drive signal to the actuatorelement, the multi-frequency drive signal comprising a cooling frequencycomponent and an acoustic frequency component superimposed on thecooling frequency component; wherein the cooling frequency componentcauses a cooling jet to eject from the opening of the body; and whereinthe acoustic frequency component produces a desired audible output. 2.The synthetic jet assembly of claim l wherein the cooling frequencycomponent comprises a frequency that is undetectable by a human ear. 3.The synthetic jet assembly of claim 1 wherein the cooling frequencycomponent is less than approximately 400 Hz.
 4. The synthetic jetassembly of claim 1 wherein the cooling frequency component is greaterthan approximately 20,000 Hz.
 5. The synthetic jet assembly of claim 1wherein the acoustic frequency component comprises at least onefrequency in a range of approximately 500-20,000 Hz.
 6. The syntheticjet assembly of claim 1 wherein the acoustic frequency componentgenerates an audible alert.
 7. The synthetic jet assembly of claim 1wherein the acoustic frequency component generates a verbal message. 8.The synthetic jet assembly of claim 1 wherein the acoustic frequencycomponent is approximately 180 degrees out of phase of a frequency of aknown ambient noise condition.
 9. The synthetic jet assembly of claim 1wherein the control unit is further configured to: receive an outputfrom a microphone indicative of an ambient noise condition; apply adigital signal processing (DSP) algorithm to determine anoise-cancelling frequency, the noise-cancelling frequency having afrequency and phase configured to cancel the ambient noise condition;and transmit the acoustic frequency component of the multi-frequencydrive signal at the noise-cancelling frequency.
 10. The synthetic jetassembly of claim 1 wherein the body of the synthetic jet comprises atleast one flexible plate; and wherein the actuator element is coupled tothe at least one flexible plate.
 11. A method of manufacturing asynthetic jet assembly comprising: providing a synthetic jet body thatencircles a volume; forming an orifice in the synthetic jet body tofluidically couple the volume to a gas outside the volume; coupling anactuator element to a flexible surface of the synthetic jet body; andelectronically coupling a controller assembly to the actuator element,wherein the controller assembly is programmed to: generate a first drivesignal comprising an inaudible frequency component that causes a coolingjet to expel from the orifice; generate a second drive signal comprisingan audible frequency component that generates a desired acoustic output;combine the first and second drive signals to form a combined drivesignal; and transmit the combined drive signal to the actuator element.12. The method of claim 11 further comprising: detecting an ambientnoise; identifying a noise-cancelling frequency to cancel the ambientnoise; and generating the second drive signal at the noise-cancellingfrequency.
 13. The method of claim 11 further comprising generating thesecond drive signal to produce at least one of a server message, andalarm, and a verbal announcement.
 14. The method of claim 11 furthercomprising generating the first frequency component in a range ofapproximately 10-400 Hz.
 15. The method of claim 11 further comprisinggenerating the second frequency component in a range of approximately500-4,000 Hz.
 16. An electronic apparatus comprising: a synthetic jetcomprising: a housing having an orifice formed therein for introducing afluid from outside the housing into a cavity of the housing andexpelling a cooling jet therefrom; and a piezoelectric actuator coupledto the housing; a drive unit configured to drive the piezoelectricactuator; a control unit configured to transmit a multi-frequency drivesignal to the drive unit; an electronic component configured to becooled by the cooling jet; and wherein the multi-frequency drive signalcomprises a cooling frequency component selected to generate the coolingjet and an acoustic frequency component selected to generate an audibleacoustic output.
 17. The electronic apparatus of claim 16 wherein thecooling frequency component is less than approximately 400 Hz.
 18. Theelectronic apparatus of claim 16 wherein the acoustic frequencycomponent is greater than approximately 500 Hz.
 19. The electronicapparatus of claim 16 wherein the control unit is programmed to operateaccording to a noise-cancelling mode.
 20. The electronic apparatus ofclaim 16 wherein the control unit is programmed to operate according toan audio-output mode.
 21. The electronic apparatus of claim 16 whereinthe electronic component comprises a light emitting diode.
 22. Theelectronic apparatus of claim 16 wherein the drive unit is directlycoupled to a surface of the synthetic jet.